Prostaglandins, a family of potent biological agents derived from essential fatty acids, function as mediators of intercellular responses via interaction with the nucleotide cyclases. In this project, previously developed tissue culture procedures will be used to study prostaglandin synthesis at the cellular level from labelled essential fatty acids. Since the original application was submitted, Samuelsson has reported that transformation of hamster kidney cells by oncogenic viruses results in marked changes in prostaglandin production. As an immediate goal, this study will concentrate on confirming these findings. Procedures for isolation and determination of small quantities of prostaglandins synthesized from essential fatty acids of high specific activity have been worked out. The methods have been validated by determination of picogram quantities of 3zH-PGE2 and PGF2 alpha in culture fields. Recent work has shown that the prostaglandin endoperoxide intermediates are approximately 100 times more potent than the prostanglandins themselves, and may be the true effectors. Methods are being developed to determine their metabolites (PHD and HHT) as a measure of overall endoperoxide formation. These procedures will be used to characterize endoperoxide and prostaglandin production by contact inhibited human fibroblasts and their transformed counterparts. If Samuelsson's results are confirmed then the investigation will focus on identifying the enzymatic defect in the prostaglandin regulatory mechanism in transformed cells. It is expected that these studies will provide basic information on the regulation of prostaglandin synthesis at the cellular level. BIBLIOGRAPHIC REFERENCES: Differential Separation of Thromboxanes from Prostaglandins by One and Two-Dimensional Thin Layer Chromatography. J.M. Bailey, R.W. Bryant, S.J. Feinmark, and A.N. Makheja, Prostaglandins, March, 1977. Differential Separation of Thromboxanes and Prostaglandins in Platelets and Cultured Human Lung Cells. R.W. Bryant, S.J. Feinmark, A.N. Makheja, and J. Martyn Bailey, Am. Soc. Biol. Chem. (in press) 1977.